Method for tibial nail insertion

ABSTRACT

A method for implanting a longitudinal intramedullary nail into the tibia comprises inserting the tibia nail along a plane of symmetry through the tuberositas tibiae. Thereby, the tuberositas tibiae can be used during nail insertion to correctly align the nail and the target arm to the symmetry plane of the bone. This means, that the whole construct, the nail attached to the target arm, has to be inserted in external rotation.

BACKGROUND OF THE INVENTION

The invention generally relates to methods for tibial nail insertion. Inparticular, the invention relates to a method for implanting alongitudinal intramedullary nail into a tibia.

Tibial nailing often requires intensive hammering during insertion whichmight cause iatrogenic fractures.

Getting the rotation correct after intramedullary nailing is a clinicalchallenge, especially for the femur. However, tibial malrotation afterintramedullary nailing is likely more common than reported. The cases ofthree patients who incurred symptomatic rotational deformities afterclosed intramedullary nailing are reported in Kevin M. Kahn, M D, et al.“Malrotation after locked intramedullary tibial nailing: Three casereports and review of the literature” (The Journal of TRAUMA, Vol. 53,Number 3, pages 549 to 552). Today, the rotation of a fractured tibia iscompared to its non-fractured counterpart, respectively. The rotation isgenerally evaluated measuring the difference in torsion. The range ofacceptable malrotation may be less than 15 degrees.

However, the shape of the tibia is unique. The tibia may have arotational mismatch between its proximal and distal ends and the anklejoint is externally rotated relative to the proximal part of the tibia(Hideki Mizu-uchi et al. “The effect of ankle rotation on cutting of thetibia in total knee arthroplasty” (The Journal of Bone & Joint Surgery2006; 88:2632-2636)).

For a better understanding, it is noted that the proximal end of thebone is the end of the bone being oriented toward the heart of the humanbody. The distal end of the bone is the end of the bone being orientedaway from the heart of the human body. An intramedullary nail may be atibia nail, wherein the intramedullary nail comprises a non-driving endand a driving end. The non-driving end is the end of the nail whichfirstly enters the intramedullary channel of a bone. Entering a bonefrom the proximal end of the bone is denoted as antegrade entering.Entering a bone from the distal end of the bone is denoted as retrogradeentering. Consequently, a nail adapted to be implanted from the proximalend of the tibia may be denoted as antegrade tibial nail.

A tuberositas tibiae plane is a plane defined by the tuberositas tibiae,i.e. the tip most protruding to the front at the proximal end of thetibia, the entry point into the medullary channel and the axis of themedullary channel inside the tibia. Furthermore, the sagittal planerelated to the tibia means a vertical plane orientated from the front tothe back (anteroposterior) in a natural position of the leg relative tothe chest of a human, for example when the lower leg is tensionlesslyplaced on a table surface with the toes orientated upwardly.Accordingly, the tuberositas tibiae plane is slightly inclined, i.e.externally rotated approximately between 13 degrees and 37 degreesrelative to the sagittal plane.

BRIEF SUMMARY OF THE INVENTION

A smoother nail design with obtuse bends or even curvatures instead ofacute-angled bends may provide improved insertion characteristics, avoidhammering and thus improve the clinical outcome.

Trying to understand the anatomy of the tibia is the key to facilitatethe nailing procedure and optimize the surgical technique. None of thecommon three anatomical planes, not even the sagittal plane, can be usedto divide the tibia into two symmetric halves.

In morphologic investigations with regard to distinctive landmarks, atuberositas tibiae plane, that is a natural symmetry plane of the tibiahas been identified. The cross section around the diaphysis forms anirregular triangle. The symmetry plane runs through the triangle's coneend represented by the tuberositas tibiae (TT) and it's elevatedcontinuation to the distal part.

The idea is to insert tibia nails along the described tuberositas tibiaeplane. Thereby, the tuberositas tibiae can be used during nail insertionto correctly align the plane of the nail containing the radius of thecurved nail portion and the target arm to the symmetry plane of thebone. This means, that the whole construct, the nail attached to thetarget arm, has to be inserted in external rotation.

In a further study, it has been determined that a nail with aretro-curved axis, a constant radius of curvature would optimally fitthe medullary canal, if the nail is inserted according to theabove-described procedure. This radius of curvature in the naturalsymmetry plane of the tibia extends between 2000 mm and 3000 mm(preferably 2500 mm). Either a constant radius or any approximation (dueto straight driving and non-driving ends with tangential connections tothe curved part) within the given radius of curvature range would fitthe medioposterior curvature of the tibia.

In summary, nailing the tibia along its medioposterior symmetry planewill offer the following benefits:

-   1) The approach permits not only a design for a dedicated left and a    dedicated right nail, but also a universal design for combined left    and right nails with an either constant retro-curved radius or a    smooth connection between the established Herzog bend of the nail,    its shaft and possible distal bend. The smooth design in turn may    improve the insertion characteristics significantly, avoid intensive    hammering and iatrogenic fractures which remains to be verified.-   2) Owing to the triangular shaped tibia shaft, drilling for all    proximal and distal mediolateral screws will be carried out more    perpendicular to the medial cortex preventing sliding of the drill.-   3) Additionally, the drilling and locking procedure will be    simplified for the surgeon due to the laterally orientated target    arm and thus the external dislocation of the operating field with    better accessibility.-   4) In case of a universal nail design for a combined left and right    nail, all screws in the tibial plateau have to be placed symmetric    to the longitudinal nail axis at an angle of between 40 and 50    degrees, preferably a 45 degrees angle between both proximal screws    and symmetric plane, in order to guarantee that their tips penetrate    the cortex in equivalent spots but at slightly different heights if    the whole construct is rotated left and right. These new screw    trajectories in the tibial plateau also reduce the risk of    penetrating the tibiofibular joint.-   5) Furthermore, this principle is considered to be used for control,    restoration and adjustment of the correct rotation. Obviously, there    seems to be a dependency between the natural rotation of the ankle    and the natural symmetry plane of the tibia defined by the    tuberositas tibiae. The idea is to use this correlation to control    the rotation. This landmark-based approach, i.e. orienting the    tuberositas tibia to the natural external rotation of the ankle    during fracture reduction, is not geared to the healthy contra    lateral side and will potentially be more accurate, reduce operation    room time and thus improve the clinical outcome. The technique of    the present invention is thus not geared to the healthy contra    lateral side and will potentially be more accurate, reduce operation    room time and thus improve the clinical outcome.

According to a first embodiment of the invention, a method forimplanting a longitudinal intramedullary nail into the tibia, comprisesthe steps of providing a longitudinal intramedullary nail having asection with a curvature, which curvature has a predetermined radius;identifying the tuberositas tibiae plane; aligning the intramedullarynail, such that the radius of the intramedullary nail lies in thetuberositas tibiae plane; and inserting the intramedullary nail into amarrow (medullary) channel of the tibia.

According to an embodiment of the invention, the intramedullary nail isan intramedullary tibia nail. According to another embodiment of theinvention, the radius of the nail is between 2000 mm and 3000 mm. Theradius may also be between 2400 mm and 2600 mm. Furthermore, the radiusmay be about 2500 mm.

The curvature of the intramedullary nail section may correspond to acurvature of the marrow channel of the tibia into which theintramedullary nail is to be inserted.

Accordingly, it depends on the actual anatomy of the fractured tibiawhat radius of the tibia nail should be preferred.

According to a further embodiment of the invention, the method furthercomprises the step of placing screws in a tibia plateau at the proximalend of a tibia into which the intramedullary nail is to be inserted inan angle of for example 40 degrees to 50 degrees, depending on theactual position and orientation of transverse holes in the proximalportion of the intramedullary nail.

According to a second embodiment of the invention, a method forimplanting a longitudinal intramedullary nail into the tibia, comprisesproviding a longitudinal intramedullary nail having a section with acurvature, which curvature has a predetermined radius; identifying asagittal plane of the tibia; aligning the intramedullary nail, such thatthe radius of the intramedullary nail lies in a plane being inclinedexternally rotated by an angle between 13 degrees to 37 degrees withrespect to the sagittal plane of the tibia; and inserting theintramedullary nail into a marrow (medullary) channel of the tibia,wherein the intramedullary nail may be an intramedullary tibia nail.

According to an embodiment of the invention, the angle is between 17degrees and 33 degrees. The angle may also be between 21 degrees and 26degrees. Furthermore, the angle may be about 24 degrees. It will beunderstood, that the angle of rotation differs due to the actual anatomyof a specific tibia.

The curvature of the intramedullary nail section may correspond to acurvature of the marrow channel of the tibia into which theintramedullary nail is to be inserted.

Also with respect to this aspect of the invention, the radius may bebetween 2000 mm and 3000 mm. The radius may also be between 2400 mm and2600 mm. Furthermore, the radius maybe about 2500 mm.

According to an embodiment of the invention, the method furthercomprises the step of placing screws in a tibial plateau of a tibia intowhich the intramedullary nail is to be inserted in an angle of forexample 40 degrees to 50 degrees, depending on the actual position andorientation of transverse holes in the proximal portion of theintramedullary nail.

These aspects defined above and further aspects, features and advantagesof the present invention can also be derived from the examples of theembodiments to be described hereinafter and are explained with referenceto the examples of the embodiments to which the invention is notlimited.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be detailed by way of exemplary embodiments withreference to the attached drawings.

FIG. 1 shows an example of a left tibia viewed in a lateral to medialdirection.

FIG. 2 shows a left tibia with a tuberositas tibiae plane perpendicularto the drawing sheet.

FIG. 3 shows a left tibia with a sagittal plane perpendicular to thedrawing sheet.

FIG. 4 shows a top view of a proximal end of a left tibia.

FIG. 5 shows a top view of a proximal end of a right tibia.

FIG. 6 is a side view of a tibia nail according to the invention.

FIG. 7 is a front view of a tibia nail according to the invention.

FIG. 8 is a top view of a target arm relative to a tibia plateau.

FIG. 9 is a top view is the rating an orientation of a target arm duringan insertion according to the invention.

FIG. 10 is a flowchart of embodiments of a method according to theinvention.

It is noted that the illustration of the drawings is only schematicallyand not to scale. In different figures, similar elements are providedwith the same reference signs.

DETAILED DESCRIPTION

In the following, FIGS. 1 to 5 are described illustrating specificanatomic aspects of a tibia and orientations of these aspects at atibia, relevant for the understanding of the invention.

FIG. 1 shows the outer contour of a tibia bone 201 with a proximal end210 of the tibia and a distal end 220 of the tibia. The tibia in FIG. 1is shown substantially from a medio-lateral direction.

As indicated by the arrows A-A in FIG. 1, the tibia in FIG. 2 is shownsubstantially from the front (anterior), wherein the tibia 201, in thisview, includes a tuberositas tibiae 202. Furthermore, the tuberositastibiae plane 40 extending through the tuberositas tibiae 202 isindicated in FIG. 2.

In FIG. 3 the tibia is shown together with a sagittal plane 50. Thetibia 201 includes proximal end 210, tuberositas tibiae 202, and distalend 220.

FIG. 4 is a view in the direction C-C (as indicated in FIG. 2), i.e. atop view on the proximal end of a left tibia. FIG. 5 is a top view onthe proximal end of a right tibia. In both figures, the tuberositastibiae plane 40 is shown extending through tuberositas tibiae 202.Furthermore, possible screw insertion directions 60, 70 for lockingscrews to be introduced into the proximal end of an intramedullary nailare shown. Furthermore, a screw insertion direction 80 for amedio-lateral (ML) screw is shown. A second screw 80 a may be insertedin the ML direction which is parallel to direction 80.

FIGS. 6 and 7 are views of an intramedullary nail, i.e. of a tibia nail,in accordance with the invention. The tibia nail 1 includes a proximalend portion 10 and a distal end portion 20, wherein the distal endportion 20 is curved with a radius R. The curvature along the centralaxis of the nail lies in a single plane. In FIG. 7, the tuberositastibiae plane 40 is additionally shown. It can be seen from FIGS. 6 and7, that the curvature of the nail is formed within one plane. The radiusR is between 2000 and 3000 mm.

FIGS. 8 and 9 show a tibia 201 together with a targeting device 100comprising a targeting arm 110. In FIG. 8, targeting arm 110 isorientated parallel to a sagittal plane 50 of the tibia. Closely besidean end 52 of the targeting arm, the tuberositas tibiae 202 is visible.In FIG. 9, the targeting arm 110 of the targeting device 100 is rotatedabout the angleα so that the targeting arm is now orientated parallel tothe tuberositas tibiae plane 40. With the targeting device in anorientation relative to the tibia as shown in FIG. 9, a tibia nail maybe introduced into the medullary channel of the tibia, in accordancewith the invention.

Further shown in FIG. 9 are locking screws, two of which orientated in amedio-lateral direction, denoted with reference sign 80. Further screwsmay be introduced inclined with respect to that direction, wherein thesefurther screws may be orientated perpendicular relative to each other,as indicated in FIGS. 4 and 5.

The flowchart in FIG. 10 illustrates the principle of the stepsperformed in accordance with the invention. It will be understood thatthe steps described, are major steps, wherein these major steps might bedifferentiated or divided into several sub-steps. Furthermore, theremight be also sub-steps between these major steps. Therefore, a sub-stepis only mentioned if this step may be important for the understanding ofthe principles of the method according to the invention.

In a first step, a longitudinal intramedullary nail 1 having a curvedsection is provided wherein the curvature has a predetermined radius asdiscussed above.

In a next step, in accordance with a first embodiment of the invention,the tuberositas tibiae plane is identified. This identification isperformed by firstly identifying the tuberositas tibiae and the entrypoint into the medullary channel on the upper surface of the tibia, andsecondly by identifying the axis of the medullary channel. Thetuberositas tibiae, the entry point as well as the axis of the medullarychannel lie on the tuberositas tibiae plane.

The intramedullary nail is aligned in a following step, such that theradius of the curved section of the intramedullary nail lies in thetuberositas tibiae plane.

Alternatively, in accordance with a second embodiment of the invention,a sagittal plane of the tibia is identified.

Then, the intramedullary nail is firstly aligned with the sagittalplane, i.e. the radius of the intramedullary nail lies in the sagittalplane, and secondly is externally rotated by an angle between 13 degreesto 37 degrees with respect to the sagittal plane orientation of thetibia previously determined.

In a subsequent step, the intramedullary nail is inserted into a marrowchannel of the tibia through an entry point in the tibial plateau.

Finally, screws may further be placed in a tibia plateau of the tibiainto which the intramedullary nail is to be inserted. The actualposition and orientation of each screw depends on the actual design ofthe driving end portion of the intramedullary nail. Finally, furtherlocking screws are inserted through transverse bores in the non-drivingend portion of the nail, so that the distal portion of the tibia may bereliably fixed relative to the proximal portion of the tibia.

While the invention has been illustrated and described in detail in thedrawings and afore-going description, such illustrations anddescriptions are to be considered illustrative or exemplary and notrestrictive, the invention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practising the claimedinvention, from a study of the drawings, the disclosure and the appendedclaims. In the claims, the word “comprising” does not exclude otherelements or steps, and the indefinite article “a” or “an” does notexclude a plurality.

The mere fact that certain measures are recited and mutually differentdependent claims does not indicate that a combination of these measurescannot be used to advantage. Any reference signs in the claims shouldnot be construed as limiting the scope.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

The invention claimed is:
 1. A method for implanting a longitudinalintramedullary nail into a tibia, the method comprises: providing alongitudinal intramedullary nail having a section with a curvature,which curvature has a predetermined radius lying along a planecontaining the longitudinal axis of the nail; identifying a plane ofsymmetry through a tuberositas tibiae; wherein the tuberositas tibiae,an entry point into a marrow channel and a longitudinal axis of themarrow channel all lie on the plane of symmetry through the tuberositastibiae; aligning the intramedullary nail, such that the plane containingthe radius of the intramedullary nail section lies in the plane ofsymmetry through to the tuberositas tibiae; and inserting theintramedullary nail into the marrow channel of the tibia.
 2. The methodof claim 1, wherein the radius is between 2000 mm and 3000 mm.
 3. Themethod of claim 1, wherein the radius is between 2400 mm and 2600 mm. 4.The method of claim 1, wherein the radius is about 2500 mm.
 5. Themethod of claim 1, wherein the curvature of the intramedullary nailsection corresponds to a curvature of the marrow channel of the tibiainto which the intramedullary nail is to be inserted.
 6. The method ofclaim 1, further comprising placing two screws in a tibia plateau of thetibia into which the intramedullary nail is to be inserted at an angleof 40° to 50° with respect to the plane through the tuberositas tibiae.7. The method of claim 6 wherein a further two screws are inserted inparallel into a proximal portion of the tibia in a medial-lateraldirection.
 8. A method of implanting an intramedullary nail in a tibiacomprising: providing a longitudinally extending intramedullary nailhaving an axially extending curved portion with a center and a radiuslying in a plane extending through a longitudinal axis of the nailcurved portion; identifying a plane of symmetry extending through atuberositas tibiae of the tibia and through a medullary canal of thetibia; inserting the nail into the medullary canal with the planecontaining the radius of the intramedullary nail curved portion coplanarwith the plane of symmetry through the tuberositas tibiae.
 9. The methodas set forth in claim 8 further comprising inserting a screw in aproximal portion of the tibia in a direction oriented at 40 to 50° tothe plane containing the nail radius.
 10. The method as set forth inclaim 9 further comprising inserting a screw in the proximal portion ofthe tibia in a direction perpendicular to the plane containing the nailradius.
 11. A method for implanting a longitudinal intramedullary nailinto a tibia, the method comprises: providing a longitudinalintramedullary nail having a section with a curvature, which curvaturehas a predetermined radius lying in a plane containing a longitudinalaxis of the nail section with a curvature; identifying a tuberositastibiae plane of symmetry by identifying a tuberositas tibiae and anentry point into the marrow channel on an upper surface of the tibia andidentifying a longitudial axis of the marrow channel; aligning theintramedullary nail, such that the plane containing the radius of theintramedullary nail lies in the tuberositas tibiae plane of symmetry;and inserting the intramedullary nail into the marrow channel of thetibia.
 12. The method of claim 11, wherein the tuberositas tibiae, theentry point into the marrow channel and a longitudinal axis of themarrow channel lie on the tuberositas tibiae plane.
 13. The method ofclaim 11, wherein the radius is between 2000 mm and 3000 mm.
 14. Themethod of claim 11, wherein the radius is between 2400 mm and 2600 mm.15. The method of claim 11, wherein the radius is about 2500 mm.
 16. Themethod of claim 11, wherein the curvature of the intramedullary nailsection corresponds to a curvature of the marrow channel of the tibiainto which the intramedullary nail is to be inserted.
 17. The method ofclaim 11, further comprising placing two screws in a tibia plateau ofthe tibia into which the intramedullary nail is to be inserted at anangle of 40° to 50° to the tuberositas tibiae plane.
 18. The method ofclaim 17 wherein a further two screws are inserted in parallel into aproximal portion of the tibia in a medial-lateral direction.
 19. Amethod for implanting a longitudinal intramedullary nail into a tibia,the method comprises: providing a longitudinal intramedullary nailhaving a section with a curvature, which curvature has a predeterminedradius lying along a plane containing a longitudinal axis of the nail inthe section with the curvature; identifying a plane through atuberositas tibiae that defines a proximal tibial medial-lateralsymmetry; aligning the intramedullary nail, such that the planecontaining the radius of the intramedullary nail section with thecurvature is coplanar with the tuberositas tibiae symmetry plane; andinserting the intramedullary nail into a marrow channel of the tibia.20. The method of claim 19, wherein the tuberositas tibiae, an entrypoint into the marrow channel and a longitudinal axis of the marrowchannel all lie on the tuberositas tibiae symmetry plane.